Fig. 3.

Control experiments demonstrating membrane impermeability of labeling reagents. PE-containing and PE-deficient cells derived from two different host backgrounds (JP6488 and AD93) were labeled with 100 µM MPB (A) or in the presence of varying concentrations of MPB or PMEOB (B) at room temperature for 5 min. In (A), cells were treated as indicated (+) with a final concentration of 0.5% toluene prior to MPB treatment. The cells were lysed with detergent and the cytoplasmic fraction retained, after removal of the membrane fraction by centrifugation, for immunoprecipitation with anti-LacZ polyclonal antibody. The immunoprecipitates were subjected to SDS-PAGE and biotinylated protein was detected using avidin-HRP and chemiluminescence.